I think it would also help if we could reach an agreement over the terms "stable" and "good quality" and "everything is working" because they are highly subjective.
For me I'd add a class; "Set-top-box quality"
It would mean that no judder and studder on HD-quality. With VDPAU the problem still might be "50Hz vs 50.02Hz" -thing so you cannot get frame accurate display. With every 5 seconds you might have duplicated display of frame or dropped frame. This is not acceptable by my standards. Typically "Set-top-boxes" can display frame accurate.
You can easily look your own modeline and dump it to a timings analyzator. http://www.tkk.fi/Misc/Electronics/faq/vga2rgb/calc.html
From MythTV wiki:
# Modeline "1920x1080@50" 148.500 1920 2448 2492 2640 1080 1084 1089 1125 +hsync +vsync
This gives exact 50Hz 1080p mode. But does your VGA-cards internal clock generator allow exactly 148.500MHz. If VGA can only generate f.ex 148.460MHz clock then you have 49.99Hz output signal. Also is pulse width divisable by 8 etc.
- Jori